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甲状腺功能减退 Hypothyroidism. 复旦大学医学院内分泌科 李 益 明. Hypothalamic-pituitary-thyroid axis. O verview. Clinical syndrome Slowing down of metabolism Slowing of growth and mental retardation in infants and children Generalized slowing down of organism Deposition of glycosaminoglycans in skin and muscle
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甲状腺功能减退Hypothyroidism 复旦大学医学院内分泌科 李 益 明
Overview • Clinical syndrome • Slowing down of metabolism • Slowing of growth and mental retardation in infants and children • Generalized slowing down of organism • Deposition of glycosaminoglycans in skin and muscle • Reversible with therapy
Etiology and Classifcation • Primary(thyroid failure) • Hashimoto’s thyroiditis • Iodide deficiency or excessive • Radioactive iodine therapy for GD • Subtotal thyroidectomy • Subacute thyroiditis • Secondary: pituitary deficit • Tertiary: hypothalamic dysfunction • Peripheral resistance to thyroid hormone
Pathogenesis • Affects each tissue • Accumulation of glycosaminoglycans (hyaluronic acid) • Not to excessive synthesis • But decreased destrution • Increased capillary permeability • Interstitial edema • Skin • Heart muscle • Striated muscle
Adults • Symptoms • Easy fatigability • Coldness • Weight gain • Constipation • Menstrual irregularities • Signs • Cool, rough, dry skin • Puffy face and hands • Hoarse and husky voice • Slow reflexes • Yellowish color skin
Clinical Features • Cardiovascular signs • Impaired myocardium contraction • Bradycardia • Diminished cardiac output • ECG: low voltage of QRS, P, T waves • Pericardial effusion • Coronary artery disease • Cardiac angina(Replacement therapy aggravate )
Clinical Features • Pulmonary function • Shallow, slow respiration • Respiratory failure • Intestinal peristalsis • Markedly slowed • Constipation • Renal function • Decreased glomerular filtration
Clinical Features • Anemia • Impaired hemoglobin synthesis • Menorrhagia and Absorption of iron • Folate deficiency • Pernicious anemia • Nuromuscular system • Muscle weakness • Slow reflexes • Central nervous system symptoms • Inability to concentrate • Anovulatory cycles and infertility • Depressed
Symptoms of hypothyroidism Symptoms % of cases Weakness 99 Dry skin 97 Coarse skin 97 Lethargy 91 Slow speech 91 Edema of eyelids 90 Sensation of cold 89 Decreaseed sweeting 89 Cold skin 83 Thick tongue 82 Edema of face 79 Coarseness of hair 76 Pallor of skin 67 Memory impairment 66
Symptomsof hypothyroidism Symptoms % of cases Constipation 61 Gain in weight 59 Loss of hair 57 Pallor of lips 57 Dyspnea 55 Peripheral edema 55 Hoarseness or aphonia 52 Anorexia 45 Nervousness 35 Menorrhagia 32 Palpitation 31 Deafness 30 Precordial pain 25
Myxedema coma • Frequently in obese elderly woman • Yellowish skin • Large tongue • Thin hair • Bradycardia • Marked hypothermia • Lethargy progressing to stupor or coma • Hypoventilation • Hypotension • Shock
Cretinism • Etiology • Low iodide intake and endemic goiter • Ectopic thyroid gland • TSH-R Ab[block] from mother • Inherited defects in thyroid hormone • Iodide,antithyroid drugs,radioactive iodine • Symptoms • Respiratory difficulty • Cyanosis • Jaundice • Poor feeding
Hypothroidism in childen • Retarded growth • Mental retardation • Precocious puberty
Laboratory Findings • FT4: • uTSH: • sensitive to detect 0.01u/mL • Most sensitive • Most convenient • Most specific • FT3: • Variable • May be within the normal range • TPOAb、TgAb: AITD (autoimmune thyroid disease) • TC
Diagnosis Symptoms+Signs FT4 +TSH or N FT4 +TSH Secondary hypothyroidism Primary hypothyroidism If ? TRH test Excessive response Normal type response No response Pituitary lesion Primary hypothyroidism Hypothalamic lesion
Drugs for hypothyroidism LT4 Desiccated thyroid Component T4 T4+T3 high ratio of T3 to T4 Dose 50g 40mg Intensity 50 g = 30mg Initial dosage 25~50 g 20mg Maintenaning dosage 50~150 g 40~120mg Half-life 7 days 1 days
Institution of replacement therapy • Full adrenal support first if with concomitant adrenal insufficiency • Beginning with low dosage • Degress of hypothyroidism • Age • General health • Increase ½ tablet weekly • Needs 6 weeks before equilibration • Use powdered thyroid gland for myxedema coma • Monitoring FT4 and TSH • TSH will be suppressed in normal range in 3 mo
Side effects • No allergy • Overdosage • Arrhythmia • Paroxyamal atrial tachycardia • fibrillation • Insomnia • Tremor • Restleness • Excessive warmth